The present invention relates, in general, to retaining mechanisms for use with implants that, for example, prevent back-out of a fixation member(s) inserted into the implant.
In cases of spinal fusion, as an example, typically a spacer or other intervertebral implant is inserted into the patient to affect fusion across one or more levels of the spine. The spacer or other implant generally engages adjacent vertebral bodies to fuse and immobilize the site and mitigate patient discomfort. In some instances, screws are inserted into holes in the spacer or implant to retain the spacer or implant in place. Frequently, without a screw back-out mechanism, it is possible for such screws to come loose from the spacer or implant, causing the spacer or implant to become dislodged or unstable in the body. As such, various screw-retaining devices have been designed to prevent back-out of screws.
For instance, spacers currently offered in the industry include a back-out prevention mechanism in the form of a set screw(s) that, when rotated, covers a portion of multiple bone screws inserted through the spacer and into bone. Due to the set screw(s) covering the bone screws, the latter is prevented from backing out of connection with the spacer. When not rotated to cover the bone screws, the set screw(s) is of a geometry to allow insertion of the bone screws through holes in the spacer. With these types of constructions, however, it is possible for the set screw(s) to itself become dislodged after implantation, thereby affecting retaining of the bone screws. In other spacer constructions, bone screws are inserted into the spacer, and a circular locking cover is screwed into the spacer to cover the bone screws and prevent back-out.
Although mechanisms for preventing screw back-out have been developed, as described above, there remains a need for a comprehensive and effective system for preventing screw back-out when a bone screw(s) is inserted into a spacer or other implant device.